Loop - Pool on an elliptical table.The ellipse has two significant points, called focuses, which have a remarkable geometrical property that is almost always explained using the example of an imaginary pool table.
"If a pool table is the shape of an ellipse, then a ball shot from one focus will always rebound to the other focus no matter in which direction the ball is shot."
That sounded interesting! Wouldn’t it be fun, I thought, if I could build one of these imaginary tables?
So I did.
posted by dng
on Jul 26, 2015 -
22 comments

Imperfect Congruence - It is a curious fact that no edge-to-edge regular polygon tiling of the plane can include a pentagon ... This website explains the basic mathematics of a particular class of tilings of the plane, those involving regular polygons such as triangles or hexagons. As will be shown, certain combinations of regular polygons cannot be extended to a full tiling of the plane without involving additional shapes, such as rhombs. The site contains some commentary on Renaissance research on this subject carried out by two renowned figures, the mathematician-astronomer Johannes Kepler and the artist Albrecht Dürer.[more inside]
posted by Wolfdog
on Jan 14, 2015 -
16 comments

So if you had been reading about all this 200 years ago, there would have been at least two important differences from now. One is that your Internet connection would have been considerably slower. The other is that you might have learned in school or elsewhere that Ceres was a planet.

Two enjoyable chapters [PDF, 33 pages] from the book Math from Three to Seven: The Story of a Mathematical Circle for Preschoolers. "This book does not purport to show you how to create precocious high achievers. It is just one person's story about things he tried with a half-dozen young children."
posted by Wolfdog
on Dec 29, 2014 -
11 comments

The law appeared in full form two decades later, when the mathematicians Craig Tracy and Harold Widom proved that the critical point in the kind of model May used was the peak of a statistical distribution. Then, in 1999, Jinho Baik, Percy Deift and Kurt Johansson discovered that the same statistical distribution also describes variations in sequences of shuffled integers — a completely unrelated mathematical abstraction. Soon the distribution appeared in models of the wriggling perimeter of a bacterial colony and other kinds of random growth. Before long, it was showing up all over physics and mathematics.
“The big question was why,” said Satya Majumdar, a statistical physicist at the University of Paris-Sud. “Why does it pop up everywhere?”

The Nature of Computation - Intellects Vast and Warm and Sympathetic: "I hand you a network or graph, and ask whether there is a path through the network that crosses each edge exactly once, returning to its starting point. (That is, I ask whether there is a 'Eulerian' cycle.) Then I hand you another network, and ask whether there is a path which visits each node exactly once. (That is, I ask whether there is a 'Hamiltonian' cycle.) How hard is it to answer me?" (via) [more inside]
posted by kliuless
on Dec 1, 2012 -
19 comments

"We have little trouble recognizing that a chess grandmaster’s victory over a novice is skill, as well as assuming that Paul the octopus’s ability to predict World Cup games is due to chance. But what about everything else?" [Luck and Skill Untangled: The Science of Success]
posted by vidur
on Nov 20, 2012 -
16 comments

Morton and Vicary on the Categorified Heisenberg Algebra - "In quantum mechanics, position times momentum does not equal momentum times position! This sounds weird, but it's connected to a very simple fact. Suppose you have a box with some balls in it, and you have the magical ability to create and annihilate balls. Then there's one more way to create a ball and then annihilate one, than to annihilate one and then create one. Huh? Yes: if there are, say, 3 balls in the box to start with, there are 4 balls you can choose to annihilate after you've created one but only 3 before you create one..." [more inside]
posted by kliuless
on Jul 21, 2012 -
78 comments

A Brief History of Mathematics is a BBC series of ten fifteen-minute podcasts by Professor Marcus du Sautoy about the history of mathematics from Newton and Leibniz to Nicolas Bourbaki, the pseudonym of a group of French 20th Century mathematicians. Among those covered by Professor du Sautoy are Euler, Fourier and Poincaré. The podcasts also include short interviews with people such as Brian Eno and Roger Penrose.
posted by Kattullus
on Dec 1, 2010 -
11 comments

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